A woman died from a heart attack on a subway train in the Bronx on Saturday morning. First responders had to chase the northbound train for several stops before reaching her, according to law enforcement officials and sources.

The 46-year-old woman was discovered unconscious on a 5 train at the East 180th Street Station close to Morris Park Avenue at approximately 11:56 a.m., the NYPD reported.

Police said they responded to the scene after receiving multiple calls from passengers notifying them of the startling incident.

Reports indicate that the woman suffered cardiac arrest at the Simpson Street Station. First responders rushed to that station only to discover that the train had moved on with the critically ill woman still onboard. The medics eventually found her at the East 180th Street station, which was four stops away.

The unidentified woman was transported to Montefiorie Hospital in the Bronx where she was pronounced dead, police said. 

The city medical examiner’s office will officially determine her cause of death.

An investigation is ongoing, police said.